Click a hiking trail to see its name, color, network and distance

The Waymarked Trails raster overlay has no queryable features (just
pixels), so this answers "what trail is this" with a one-off Overpass
query on click instead: way(around:40m) finds candidate ways, then
rel(bw) walks backward to their parent route=hiking relations. Overpass
has permissive CORS, so this runs straight from the browser, no server
proxy needed — verified against a real KST route in the Tatras.

Route length isn't tagged directly, so it's summed from each member
way's own geometry (measure.js's existing haversine lineLength, now
exported and reused rather than duplicated). The colour tag is only
ever used as a CSS background after matching a strict hex/word regex —
untrusted free text otherwise.

public/js/measure.js

@@ -317,7 +317,9 @@ function haversine([lng1, lat1], [lng2, lat2]) {
   return 2 * EARTH_RADIUS_M * Math.asin(Math.sqrt(a));
 }
 
-function lineLength(points) {
+// Exported — also used by hiking_trails.js to total up an OSM route
+// relation's member ways into one distance, same haversine-sum approach.
+export function lineLength(points) {
   let total = 0;
   for (let i = 1; i < points.length; i++) total += haversine(points[i - 1], points[i]);
   return total;
@@ -347,7 +349,8 @@ function polygonArea(points) {
   return Math.abs((area * EARTH_RADIUS_M * EARTH_RADIUS_M) / 2);
 }
 
-function formatDistance(meters) {
+// Exported — also used by hiking_trails.js's route-details popup.
+export function formatDistance(meters) {
   if (meters === 0) return "";
   return meters >= 1000 ? `${(meters / 1000).toFixed(2)} km` : `${Math.round(meters)} m`;
 }